1. Field of the Invention
The presented invention relates to a light tube or lamp actuating facility, particularly to a lamp actuating facility for evenly or uniformly driving or actuating a number of light tubes or lamps such as liquid crystal display (LCD) light devices or display panels.
2. Description of the Prior Art
Typical LCD display panels employ various kinds of discharge lamps, such as cold cathode fluorescent lamps (CCFL) as the backlight source for the display panels, and employ an inverter circuit to drive the discharge lamps.
In larger LCD display panels, a number of lamps or light tubes are required and to be installed for providing the required brightness. When a number of lamps are installed in the larger LCD display panels, a single transformer or driving or actuating circuit is not so effective on performance to actuate or drive two or more discharge lamps that are coupled in parallel with each other.
For example, the impedances of the discharge lamps may be different from each other, and may seriously influence the flowing of the electricity through the discharge lamps; i.e., the electricity may not be evenly flown through the discharge lamps, such that the discharge lamps may not be suitably driven or actuated or energized.
When the electric current is less than the required amount, the discharge lamps may not be suitably driven or actuated or energized to the required brightness, and the brightness in different portions or areas of the larger LCD display panels may be different from each other, and may seriously decrease the uniformity of the display panels.
On the contrary, when the electric current is greater than the predetermined amount, the discharge lamps may be over-energized and the working life of the discharge lamps may be greatly reduced. In addition, the characteristics of the discharge lamps may be changed any time, such that the electricity may not be used to evenly energize various discharge lamps.
For example, the diameters of different discharge lamps may be different from each other, the mercury densities and/or the electrodes of different discharge lamps may also be different from each other, the pressures of different discharge lamps may also be different from each other, such that the impedances of the discharge lamps may be different from each other, and such that different discharge lamps may not be evenly energized by the typical driving or actuating circuits.
Furthermore, when the discharge lamps are initialized, various kinds of strong interferences, noises, abrupt waves, may be generated, and may directly or indirectly affect the normal operation of peripheral facilities of the display panels. The higher the voltage is applied, the higher the electromagnetic interference may be generated, and thus the higher the possibility of injuring the users and the others.
In addition, the discharge lamps of the typical LCD display panels may normally generate flashes that people may not be easily aware of and that may hurt people or may easily make people or users fatigue.
U.S. Pat. No. 4,396,872 to Nutter discloses one of the typical lamp actuating facility comprising a number of lamps or groups of lamps each including an output terminal point connected to lamp current sensor, an inverter circuit (ballast) coupled to the lamp or the group of lamps.
However, Nutter fails to disclose a MOSFET coupled between the inverter circuit and the low frequency control circuit. Actually, Nutter discloses a typical close loop feedback control system having sensors to detect various values and to send the values to microprocessors, and then to control the operation condition of the inverter (ballast) itself but not to switch the output conductivity of each individual lamp, it means no light output balance control within the group of lamps.
U.S. Patent Publication No. 2004/0032223 to Henry discloses another typical power conversion circuit comprising a MOSFET coupled between an inverter circuit and a control circuit. However, Henry may not be used to evenly and uniformly drive or actuate a number of light tubes or lamps.
U.S. Pat. No. 3,916,251 to Hernandez et al. discloses one of the typical current detecting circuit comprising an integrator circuit. However, Hernandez et al. also may not be used to evenly and uniformly drive or actuate a number of light tubes or lamps.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages of the conventional lamp actuating facilities.